Textbook Question
The following sequence is a portion of the DNA template strand: TGT GGG GTT ATT
b. What are the anticodons of the tRNAs?
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26. Nucleic Acids and Protein Synthesis
Translation: Protein Synthesis
3:25 minutesProblem 68a
Textbook Question
A point mutation in the mRNA for an enzyme results in the replacement of leucine with alanine in the resulting enzyme molecule. Why does this change in amino acids have little effect on the biological activity of the enzyme?
Verified step by step guidance1
Understand the concept of a point mutation: A point mutation is a change in a single nucleotide in the mRNA sequence, which can lead to a change in the codon and potentially alter the amino acid sequence of the resulting protein.
Recognize the properties of leucine and alanine: Both leucine and alanine are nonpolar amino acids, meaning they share similar chemical properties and are likely to interact similarly within the enzyme's structure.
Consider the enzyme's structure and function: Enzymes are proteins with specific three-dimensional structures that determine their biological activity. If the replacement of leucine with alanine occurs in a region of the enzyme that is not critical for its active site or overall folding, the enzyme's function may remain unaffected.
Evaluate the impact of the mutation: Since leucine and alanine are chemically similar, the substitution may not significantly disrupt the enzyme's hydrophobic interactions or overall stability, which are crucial for maintaining its activity.
Conclude why the change has little effect: The replacement of leucine with alanine likely has minimal impact on the enzyme's biological activity because the chemical properties of the two amino acids are similar, and the mutation does not appear to affect critical regions of the enzyme.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Point Mutation
A point mutation refers to a change in a single nucleotide base pair in the DNA sequence. This can lead to the substitution of one amino acid for another in a protein, as seen in the question. Depending on the nature of the amino acids involved, such mutations can have varying effects on protein function, ranging from negligible to significant.
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Amino Acid Properties
Amino acids have distinct properties that influence protein structure and function. Leucine is a hydrophobic amino acid, while alanine is also hydrophobic but smaller in size. When a mutation results in the substitution of one hydrophobic amino acid for another, the overall structure and function of the enzyme may remain largely unchanged, especially if the active site is not affected.
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Enzyme Activity and Redundancy
Enzymes often exhibit a degree of redundancy in their active sites, allowing them to maintain functionality despite minor changes in their amino acid composition. This means that even if a specific amino acid is altered, the enzyme may still perform its biological function effectively. The robustness of enzyme activity can be attributed to the flexibility of protein structures and the ability of enzymes to accommodate slight variations.
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